The use of supplemental or enhanced illumination to modify ambient light, or light from an additional source, when performing still or motion optical image gathering is known. For example, it is often desirable to reduce the area or intensity of shadowing on an individual target. In the film, television and photographic industries, illumination of human faces is often tailored to enable a shadow free image of the face to be gathered. This may be achieved by the provision of a light source for the optical image gathering apparatus. For example, it is common to provide illumination of a small foreground area with sufficient intensity to match the background light.
Supplemental illumination may be provided by a light source either supported on a stand or mounted to the image-gathering device. The light source may comprise a single lamp or a plurality of lamps, for example arranged in a circular array. Lamps may be battery powered or mains voltage powered.
Lighting may be provided in the form of a battery powered halogen quartz light source, or a tungsten filament light with a Fresnel glass front element to focus the beam. This type of light source is commonly clamped to the top of the image-gathering device. A problem with this arrangement is that the light source is off the lens axis, which creates shadowing, and often the quality of the light is harsh. Further, on a portable image gathering device, such an off axis mounted light source modifies the centre of gravity of the light and image gathering device combination, making the apparatus unwieldy to handle. Alternatively, lighting may be provided by a mains voltage powered photoflood or halogen bulb.
A problem with both halogen and tungsten light sources is that the operating electrical requirement of the bulbs, or the physical size of the light source, is such that the light source is not portable and therefore of limited application. For example, the current draw of both these types of bulbs is too high to be provided from a portable battery supply, for example a belt, through a cable of a practical size. It is not desirable to increase the operating voltage beyond that of the industry maximum voltage standard and increasing the size of the cable would create user difficulties. In some cases, it is desirable to attach the light source to a camera dolly or crane system.